Itsuka Shikabane operates under the codename Plamya, meaning "flame" in Russian. She lives a double life as an ordinary high school student and a senior operative in a secret organization. Tall and slender with long black hair, she wears a distinctive skull-patterned eyepatch over her right eye; this eyepatch acts as a vital psychological crutch, essential for her confidence and combat effectiveness. Without it, she becomes notably timid and hesitant. On missions, her attire includes a red leotard, a black military-style coat, low-rise pants, an eye mask matching the skull motif, and she wields a sword with a rhinestone-decorated handle and decorative strap, often riding a motorcycle. As a student, she wears a standard uniform and holds the position of student council president. Personal spaces like her room display numerous photographs of Kate Hoshimiya and cat-themed items.

Her personality shifts dramatically based on context. She exhibits intense, almost obsessive affection and loyalty towards Kate Hoshimiya, viewing her as an older sister figure and emotional anchor. This devotion stems from childhood trauma: Kate comforted Itsuka at her mother Tsubaki Shikabane's funeral while appearing physically older, establishing Kate as Itsuka's source of stability. Itsuka clings to Kate tearfully exclaiming "Onee-san" during distress. Conversely, she displays aggressive, threatening, and sadistic tendencies towards most others, particularly male organization members, sparing only Roboko and Natasha. She harbors pronounced animosity towards Asuta Jimon and her aunt Kaori Hayabusa. Itsuka struggles with profound insecurity over her culinary ineptitude; her cooking is notoriously inedible, causing organization members to flee. Witnessing superior cooking skills in others triggers playful irritation.

Functionally, she serves as her organization's primary frontline combatant, specializing in swordsmanship and high-speed motorcycle pursuit. Her exceptional physical capabilities are demonstrated by effortlessly following a sprinting Asuta while walking normally. She undertakes missions alongside her father, Goro Shikabane (General Pepel). Her mother's death remains a pivotal event; afterward, Kate persuaded her to adopt the skull eyepatch as a symbol of strength, intrinsically linking it to her identity and courage. Minimal character development occurs through culinary subplots: after tasting Asuta’s cooking, she temporarily sets aside hostility to request his culinary instruction, acknowledging her deficiency. Familial connections include being Goro’s daughter and Kaori Hayabusa’s niece, with the latter relationship marked by mutual dislike. Her mother's funeral is the sole detailed familial event underpinning her psychological dependence on Kate.